Synthesis and crystal structure of a PdII complex of ortho-xylylenebis(pyridyltriazole)

The ortho-xylylenebis(pyridyltriazole) ligand coordinate with PdII giving dimeric square-planar complexes on which the Pd⋯Pd separation is 3.6184 (4) Å.


Structure description
The self-assembly of polydentate ligands with transition-metal ions to create functional metal-organic supramolecules has been of great interest in recent years. In particular, the complexation of 2-pyridyl-1,2,3-triazole chelating pockets with transition-metal ions has intensified due to the ease of synthesis of the ligands through the copper-catalyzed azidealkyne cycloaddition (CuAAC) reaction (Crowley & McMorran, 2012). We and others have studied the complexation of ortho-, meta-, and para-xylylene-bridged pyridyltriazole tetradentate ligand with Cu II (Pokharel et al., 2013(Pokharel et al., , 2014, Ni II (Pokharel et al., 2020b), Fe II (Vellas et al., 2013), Ag I (Gower & Crowley, 2010), and Cu I (Zhao et al., 2013). We have recently studied the crystal structure of 1,1-bis(pyridyltriazoylmethyl)ferrocene and its complexation with Cu I (Pokharel et al., 2020a). As an extension of this work, we were also interested in studying the complexation of ortho-xylylene-data reports bis(pyridyltriazole), o-xpt, with Pd II . Herein, we report the synthesis and crystal structure of the title compound.
The structure of the title compound consists of the cationic Pd II complex [Pd 2 (o-xpt) 2 ] 4+ lying on an inversion center, two BF 4 À anions in general positions, a dimethylformamide solvent molecule in a general position and a diethyl ether solvent molecule disordered about an inversion center (Fig. 1). In the complex, two Pd II cations are coordinated by two tetradentate o-xpt ligands, giving a dimeric macrocycle. The two pyridyltriazole units are coordinated to each metal center in a trans fashion. The Pd II centers are tetracoordinated in a square-planar geometry defined by four (N1, N2, N7 and N8) atoms of two pyridyltriazole moieties. The N-Pd-N chelating angles are N1-Pd1-N2 = 79.46 (8) and N7-Pd1-N8 = 79.75 (8) . The N(py)-Pd bonds [py is pyridine; average 2.055 (2) Å ] are slightly longer than N(trz)-Pd bonds [trz is triazole; average 1.995 (2) Å ], suggesting the triazolium N atom coordinates more strongly to the Pd center than the pyridyl N atom of the ligand. These values are typical for the reported mononuclear Pd II complex of pyridyltriazole ligands (Kilpin et al., 2011). The PdÁ Á ÁPd separation in the complex is 3.6184 (4) Å . Two phenylene moieties in the complex are in an antiparallel orientation, with an interplanar separation of 7.802 Å .
In the crystal packing, the pyridyltriazole units between two adjacent molecules are associated in a head-to-tail arrangement (the electron-rich pyridyl group of one molecule stacks over the electron-deficient triazole group of the other molecule) with an average interplanar distance of 3.364 Å , indicatinginteraction between the molecules; this is shown along the b axis in Fig. 2.

Synthesis and crystallization
To a stirred solution of [Pd(CH 3 CN) 4 ]BF 4 (0.112 mg, 0.253 mol) in acetonitrile (5 ml), o-xpt (0.100 g, 0.253 mmol) in acetonitrile (5 ml) was added dropwise. The solution was stirred for 1 h at room temperature. The volatiles were removed in vacuo. The residue was washed with dichloromethane (2 ml), followed by methanol (2 ml), and dried under vacuum to give [Pd 2 (o-xpt) 2 ](BF 4 ) 4 (0.126 mg, 74%) as a paleyellow solid. Crystals suitable for X-ray analysis were obtained by slow vapor diffusion of diethyl ether into a dimethyl-

Figure 1
The molecular structure of the title compound with the atom numbering. Displacement ellipsoids are drawn at the 50% probability level, and H atoms and disordered solvent molecules have been omitted for clarity.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1